var n,i,a,p,b:longint;
    t:int64;
    f,g:text;
begin
assign(f,'fact.in');
assign(g,'fact.out');
reset(f);
rewrite(g);
read(f,p);
t:=1;
a:=0;
for i:=1 to 30 do begin
t:=t*i;
b:=10;
while t mod b=0 do begin
a:=a+1;
b:=b*10;
end;
t:=t div (b div 10);
t:=t mod 1000000000;

if a=p then begin
 writeln(g,i);
 break;
end;
end;
close(g);
end.